Is greater temperature change within a day associated with increased emergency hospital admissions for heart failure?

BACKGROUND Although the seasonal variation and the effect of cold temperature on heart failure (HF) morbidity have been well documented, it is unknown whether the temperature variation within a day, that is, diurnal temperature range (DTR), is an independent risk factor for HF. We hypothesized that large DTR might be a source of additional environmental stress and, therefore, a risk factor for HF exacerbation. We aimed to test the association between DTR and HF hospitalization and to examine the effect modifiers, such as age, sex, and season. METHODS AND RESULTS We collected daily meteorologic data and emergency HF hospital admissions from 2000 to 2007 in Hong Kong. We used Poisson regression models to fit the relationship between daily DTR and emergency HF hospitalizations, after adjusting for the time trend, seasonality, mean temperature, humidity, and levels of outdoor air pollution. We confirmed the seasonal variation of HF with peak hospital admissions in winter in Hong Kong. The adverse effects of DTR on emergency HF admissions were observed on the current day and lasted for the following several days. Every 1°C increase of DTR at lag0 corresponded to 0.86% (95% confidence interval, 0.31%-1.43%) increment of emergency hospital admissions for HF. DTR exhibited significantly greater effect in the cool season, and on female and elderly patients. CONCLUSIONS Greater temperature change within a day was associated with increased emergency hospital admissions for HF. Health policymakers and hospitals may want to take into account the increased demand of specific facilities for susceptive population in winter with greater daily temperature variations.